Many different types of materials including fabric, paper, films, foils, and the like are formed into what is commonly known as a web. In the production, processing, or treatment of a web, the web is often moving as it progresses from one operation, such as cutting, slitting, printing, and the like, to the next operation. It is important to be able to accurately determine the position of the web as it moves so that it can be properly aligned for the various operations.
One commonly known technique for determining the position of a moving web involves detecting the position of the physical edge of the web using an ultrasonic edge detector. Several such edge detectors are described in U.S. Pat. Nos. 5,072,414, 5,274,573, and 5,834,877, all to Buisker et al. These patents all describe compact edge detectors that allow for the use of a compensation beam in addition to the position detecting beams. Despite their advantages, these edge detectors cannot be used to determine the position of webs that consist of certain types of materials that are acoustically transparent, such as non-woven fabric and mesh.
Other types of edge detectors that utilize light-type edge detectors are also known. One such edge detector is described in U.S. Pat. Nos. 6,175,419 and 6,323,948, both to Haque et al. While this system utilizes light sources, the system also includes a complex housing design and a complex lens system that is not compact in design.
A system and method for determining the position of an edge of a web that overcome these deficiencies are needed.